Electric contact grease

ABSTRACT

AN ELECTRIC CONTACT GREASE CONSISTING ESSENTIALLY OF: (A) A MAJOR AMOUNT OF DI-2-ETHYL-HEXYL SEBACATE, (B) FROM 0.5 TO 40.0 PERCENT BY WEIGHT OF POLYOXYPROPYLENE BUTYL ETHER, (C) FROM 0.2 TO 5.0 PERCENT BY WEIGHT OF AN AMINO COMPOUND AS AN ANTIOXIDANT, (d) FROM 9 TO 18 PERCENT BY WEIGHT OF LITHIUM STERATE.

July 2, 1974 AKIRA INAMI ETAL- 3,22,208

ELECTRIC CONTACT GREASE Filed April 2, 1973 LL] 900 fl Q 1: 800

I U E O 700 U L 0 Z 600- Q I 2 U 500 DA In LL 9 O EL 400 LIJ D Q 3 300- EC LL] Z LL] Q 200 LL] 2 I) w Z 100- O U NUMBER OF TIMES OF SLIDING ACTION Io United States Patent Office 3,822,208 ELECTRIC CONTACT GREASE Akita Inami, Hirakata, Sankichi Shida, Nara; Mikio Haga,

Hirakata, and Kotaro Kariya, Neyagawa, Japan, assignors to Matsushita Electric Industrial (30., Ltd., Osaka, Japan Filed Apr. 2, 1973, Ser. No. 346,794 Claims priority, application Japan, May 25, 1972,

1m. c1. o1om7/24, 7/32 US. Cl. 252-421 1 Claim ABSTRACT OF THE DISCLOSURE An electric contact grease consisting essentially of:

(a) a major amount of di-2-ethyl-hexyl sebacate,

(b) from 0.5 to 40.0 percent by weight of polyoxypropylene butyl ether,

() from 0.2 to 5.0 percent by weight of an amino compound as an antioxidant,

(d) from 9 to 18 percent by weight of lithium stearate.

FIELD OF INVENTION The present invention relates to an electric contact grease which has particular application in sliding contacts of electrical machines and apparatuses.

DESCRIPTION -OF THE PRIOR ART Conventional electric contacts in, for example, television and radio are subjected to contact failure and are responsible for problems such as sound noise, picture failure and the like.

These problems are prevented to some extent by using electric contact greases. However, conventional grease for an electric contact has not been completely satisfactory .due to the complicated nature of the phenomenon of the electric contact.

Contact failure is usually caused by oxidation, sulphurization and wear of contact metal surfaces and sludge formed by oxidation and polymerization of grease itself used for the contact. Therefore, the role of contact grease is to prevent oxidation, sulphurization and wear of contact metals so as to stabilize the electric contact resistance, to prevent noise and to lengthen the life of the electric contact.

BRIEF SUMMARY OF THE INVENTION BRIEF DESCRIPTION OF THE DRAWING The Figure shows the relationship between the number of times of sliding action and the stability of electric contact resistance.

DETAILED DESCRIPTION A contact grease according to the present invention consists essentially of a major amount of di-Z-ethyl-hexyl sebacate, 0.5 to 40.0 percent by weight of polyoxypropylene butyl ether (POPBE) C H O(CH 'CH-CH O),,H, 0.2 to 5.0 percent by weight of an amino compound as an antioxidant, and 9 to 18 percent by weight of lithium stearate.

The novel contact grease according to the present invention prevents an electric contact from failing, and ensures satisfactory contacting action for a longer time period, especially when applied to an electric contact which is composed of a contact rivet made of a metal selected from the group consisting of platinum, gold, silver, copper and their alloys as one contact, and the other contact is a plate made of nickel or nickel silver. Nickel is often used for plating a printed circuit or a contact metal because of its good chemical stability and mechanical characteristics although its electric resistivity is comparably higher.

Di-Z-ethyl-hexyl sebacate as defined herein includes commercially available material as well as pure material.

A contact grease according to the present invention comprises PORBE. It is preferable that the POPBE has 4 to 50 average mols of propylene oxide (PD) group.

The POP-BE with less than 4 mols of PO group results in contact grease which has poor antiwearing property, and higher than 50 mols results in contact grease which also has poor antiwearing property.

When the POPB-E is present in an amount lower than 0.5 percent by weight, the antiwearing property is also poor.

At an amount of POP-BE higher than 40 percent by weight, the electric contact resistance becomes unstable.

The contact grease according to the present invention also comprises an amino compound as an antioxidant, i.e. at least one member selected from the group consisting of N,N'-di-sec-butyl-paraphenylene diamine, N,N,N,N'- tetramethyl-4,4'-diamino diphenyl methane (tetra base) and N-phenyl-u-naphthyl amine.

When the amino compound is present in an amount lower than 0.2 percent by weight, electric contact resist ance is difficult to stabilize. When that amount is higher than 5.0 percent by weight, the electric contact resistance becomes higher.

The amino compound as an antioxidant not only serves to prevent the POPBE from oxidation, but at the same time decreases the wear of contact metals and stabilizes the contact resistance.

The contact grease according to the present invention also comprises lithium stearate. The lithium stearate defined herein includes commercially available material as well as pure material.

When the lithium stearate is present in an amount lower than 9 percent by weight, the grease has poor physical stability. When that amount is higher than 18 percent by weight, the antiwearing property becomes poorer.

The contact grease according to the present invention is preferably added with other additives, such as a rust inhibitor, an antisulphurizing agent, etc.

According to the present invention, a mixture of the di-Z-ethyl-hexyl sebacate, POPBE, amino compound and lithium stearate with or without rust inhibitor and antisulphurizing agent is heated at 2l0230 C. to form a homogeneous liquid.

The mixture is cooled rapidly, milled by a conventional method, and is subjected to a reduced pressure so as to remove air and foam.

The resulting greases are smooth and buttery in texture and have excellent mechanical and thermal stability.

The invention is described in the following examples, which are for the purpose of illustration and are not considered to be limitative with respect to scope or condition. In the example, g represents grams.

Example 1 A mixture of 86.2 g. of di-Z-ethyl-hexyl sebacate, 1.0 g. of POPB E having 5.0 mols of PO groups, 0.3 g. of tetra base and 12.5 g. of lithium stearate is heated at about Example 2 A mixture of 77.3 g. of di-Z-ethyl-hexyl sebacate, 8.2 g. of POPBE having 15.2 mols of PO group, 1.0 g. of N,N'-di-sec-butyl-paraphenylene diamine and 13.5 g. of lithium stearate is heated at 215 C.

The resulting mixture is treated in a way similar to that of Example 1. The test is carried out similarly to Example 1 and the test results are shown in Table 1 and in the Figure.

Example 3 A mixture of 78.5 g. of di-Z-ethyl-hexyl sebacate, 5.5 g. of POPBE having 47.5 mols of PO group, 1.8 g. of tetra base and 14.2 g. of lithium stearate is heated at 220 C.

The resulting mixture is treated in a way similar to that of Example 1. The test is carried out similarly to Example 1 and the test results are shown in Table 1 and in the Figure.

Example 4 A mixture of 48.7 g. of di-Z-ethyl-hexyl sebacate, 38.5 g. of POPBE having 23.0 mols of PO group, 1.5 g. of N,N'-di-sec-butyl paraphenylene diamine and 11.3 g. of lithium stearate is heated at 230 C.

The resulting mixture is treated in a way similar to that of Example 1. The test is carried out similarly to Example 1 and the testing result is shown in Table 1 and in the Figure.

Example 5 A mixture of 65.0 g. of di-2-ethyl-hexyl sebacate, 21.0 g. of PO-PBE having 35.2 mols of PO group, 3.5 g. of N- phenyl-a-naphthyl amine and 10.5 g. of lithium stearate is heated at 210 C.

The resulting mixture is treated in a way similar to that of Example 1. The test is carried out similarly to Example 1 and the test results are shown in Table 1 and in the Figure.

Table 1 shows the testing results of antiwearing property of the grease of Examples 1 to 5 and a commercially available conventional grease for comparison.

The test was carried out as follows.

The greases were applied to the sliding contact which comprises a combination of a movable contact rivet and fixed contact plate.

The material used for the fixed contact plate is nickel.

The radius of curvature of the top of the movable contact rivet is 2 mm. The rivet is made of at least one member selected from the group consisting of platinum, gold, silver, copper and their alloys.

The wear of the contact rivet was measured as the decreased thickness of the top of the rivet after 50 thousand times of sliding action with sliding speed of 8 cm./ sec. and sliding distance of 4 cm.

As the value of the electric contact resistance fluctuates with sliding action, the peak value of contact resistance has little meaning.

Therefore, the energy E that was consumed at the contact in a given time was counted.

4 Energy E is expressed as follows.

t 2 E f 1 Rcdt (1) i: contact current measure t: time measured I Rc: Electric contact resistance In the present case, the condition is as follows.

i=50 ma. 1:1 sec.

The reference numbers 1 to 11 in the Figure correspond to the numbers in Table 1 respectively.

Generally speaking, the difference between the contact resistance before and after sliding action should not be large in order to be used effectively for electric contact.

It is clear from the Figure that the grease according to the present invention has little difference between the contact resistance at the beginning and after 50 thousand times of sliding action.

Consequently, the grease according to the present invention provides an electric contact having a stable contact resistivity, with complete prevention of noise generation and with lengthening the life of the electric contact.

TABLE 1 Wear of Comcontact rivet (thick Test Sample of ness) N0. grease (mm.)

1 Example 1 0.032 2---" Example 2..-.-. 0.027 3 Example3 0.024 4 Example 4 0.020 5-. Example 5 0.022 6--.. Silicone grease-.. 0.060 0. 007 Ag 0.052 Ag-Cu (-10) 0. 01s 90 Au-Ag-Pt(69-216) 0 017 90 Nickel, sllver 0.014

We claim:

1. An electric contact grease consisting essentially of:

(a) a major amount of di-2-ethyl-hexylsebacate,

(b) from 0.5 to 40.0% by weight of polyoxypropylene butyl ether, wherein said polyoxypropylene butyl ether has 4 to 50 average mols of propylene oxide groups, p

(c) from 0.2 to 5.0% by weight of an amino compound selected from the group consisting of -N,N-disec butyl paraphenylene diamine, N,N,N,N'-tetramethyl-4,4'-diamino diphenyl methane and N-phenyla-naphthyl amine, as an antioxidant,

(d) from 9 to 18 percent by weightof lithium stearate.

References Cited UNITED STATES PATENTS 2,450,221 9/1948 Ashburn et al 25242.l 2,585,182 2/1952 Sterman 252-42.1 2,680,095 6/1954 -Holten et al 25242.1 2,721,844 10/1955 Culnane et al 252-42.1 3,078,229 2/ 1963 Cox 25242.1

DANIEL E. WYMAN, Primary Examiner I. VAUGHN, Assistant Examiner U.S. Cl. X.R. 25250, 518 v 

